1. Field of the Invention
This invention relates to a packaging container for containing developer sheets which are used in obtaining images by methods using pressure-sensitive, photosensitive and pressure-sensitive, or photo-sensitive and heat-sensitive sheets and also to a packaging method of the developer sheets.
2. Description of the Related Art
As shown in U.S. Pat. No. 4,399,209, developer sheets of the type mentioned above are used by superposing the same with a microcapsule-bearing sheet wherein a latent image has been formed by imagewise exposure to light and by pressing them together thereby forming a visible image on the developer sheet by color development between developer material coated on the developer sheet and materials flowed from the microcapsules.
A known packaging method comprises placing a predetermined number of developer sheets in a open-faced paper box and, after covering with a top open-faced box, wrapping with two or three strips of plastic film. This wrapping has the purpose of holding the boxes together at the time of transportation.
However, the conventional packaging container and packaging method for the developer sheets permits the developer sheets to contact with outside air. After storage over a long time, the developer on the sheet is liable to be oxidized and yellowed by the action of oxidizable materials contained in air. Using such developer sheets, desired color developing characteristics cannot be obtained with an attendant problem that the commercial value is lowered.